Handbook of Vitamin C Research

318Samar Al Sayegh Petkovšek and Boštjan Pokornyused for analytical quality control: vitamin C and vitamin E: Bucks Fluk, no. 95210;chlorophyll a: FLUKA 25739; and chlorophyll b: FLUKA 25749, respectively.Table 3. Mean annual deposition of SO 2 (μg/m 3 ) at selected locations in the period 1991-2007 (source: Rotnik, 2008)year Zavodnje Veliki Vrh Topolšica Graška gora1991 50 80 40 301992 55 76 58 421993 47 58 55 471994 49 53 34 501995* 26 49 20 271996 33 57 20 281997 42 53 18 361998 43 63 20 321999 42 72 17 322000* 31 56 18 342001 20 51 11 152002 19 51 14 162003 15 45 16 102004 8 30 6 62005 12 33 5 62006 8 20 4 62007 7 14 3 5Note: *Two desulphurization devices were installed in February 1995 and in November 2000,respectively. Bold figures exceeded the permitted levels defined by Slovene and Europeanlegislation (20 μg/m 3 ) (Official Gazzete of the Republic of Slovenia, No. 52/2002; Directive2008/50/EC of the European parliament and the Council of 21 May 2008 on ambient air qualityand cleaner air for Europe).2.3. Statistical AnalysisAll results presented in the paper represent annual mean values, calculated on the basis ofdata provided for selected five spruce trees per sampling site, sampled at ten locations in theemission area of the ŠTPP in the period 1991-2007. Microsoft Excel was used for calculationof mean values and standard errors. Existence of correlations between different parameterswas tested by calculating Spearman rank coefficient (R) using Statistica for Windows 7.1software package (StatSoft, 2006); the limit of statistical significance was set up at p < 0.05.In the following sections, all results are given as mg/g on a dry weight basis.